STUDIES ON THE COEXISTENCE OF SUBSTANCE-P WITH OTHER PUTATIVE TRANSMITTERS IN THE NODOSE AND PETROSAL GANGLIA

Visceral afferent neurons of the nodose and petrosal ganglia are immunoreactive (ir) for many neurotransmitters [e.g., substance P (SP), neurokinin A (NKA), calcitonin gene‐related peptide (CGRP), and dopamine (tyrosine hydroxylase‐ir; TH)]. Coexistence of SP‐ir with NKA‐, CGRP‐, or TH‐ir was studied in individual neurons of the rat ganglia using fluorescene immunocytochemistry. SP‐ and NKA‐ir were present in equal numbers of cells and were consistently colocalized. SP‐ and CGRP‐ir were found to be similarly distributed in scattered cells, concentrated mostly in the rostral pole of the nodose ganglion and in the petrosal ganglion. SP‐ir completely coexisted with CGRP‐ir. However, there was at least twice the number of CGRP‐ir neurons as SP‐ir neurons, and thus CGRP‐ir neurons that did not contain SP‐ir were also present. In contrast, SP‐ and TH‐ir had different distributions in both the nodose and the petrosal ganglia. SP‐ir was located in the more rostral regions of both the nodose and petrosal ganglia, whereas TH‐ir was detected throughout the entire nodose ganglion and only in the most caudal region of the petrosal ganglion. There was no coexistence of SP‐ and TH‐ir. These data demonstrate the differential localization and coexistence of putative transmitters in visceral sensory neurons in the nodose and petrosal ganglia. Copyright © 1990 Wiley‐Liss, Inc.